The long-term goal of this study is to develop an optical tomographic imaging method to assist in the diagnosis, characterization, and monitoring of joint diseases. In recent years, considerable progress has been made toward these novel imaging methods. The technology for making light transmission measurements on human subjects is now readily available and has been applied in a variety of pilot studies concerned with monitoring of blood oxygenation determination, hemorrhage detection, functional imaging of brain activity, diagnosis of Alzheimer disease, and detection of breast cancer. The application of optical tomography (OT) to imaging and diagnosis of arthritis and musculoskeletal disorders has received little attention, even though imaging of joints with OT appears less challenging than breast or brain imaging. One can expect relatively good signal to noise ratios for the transmitted light intensities because of the comparatively small dimensions of, for example, finger joints. Furthermore, changes in the optical properties of various joint components can be expected for most diseases. For example, it is known that with the onset of rheumatoid arthritis, the synovial fluid in the articular cavity becomes increasingly turbid. Therefore, as a specific example, the applicants proposed to initially apply OT to the diagnosis and monitoring of rheumatoid arthritis in the joints of the hand. There remain two key problems to be solved for a successful implementation of an optical tomographic imaging system for joints. 1) Due to the presence of the almost non-scattering synovial fluid in all joints, commonly employed diffusion-theory-based image reconstruction schemes cannot be applied. 2) Due to the strong variation in optical properties within the joints, widely used perturbation-theory approaches to the image reconstruction problem are insufficient. To overcome these deficiencies of currently available reconstruction algorithms, and to develop an optical tomographic system suitable for imaging finger joints, the applicant plans to perform the following studies: (a) Develop non-perturbation 3D-reconstruction algorithm that uses the theory of radiative transfer for the prediction of detector readings. (b) Determine sensitivity of optical tomographic image system to changes in the optical properties of various joint components and evaluate accuracy of image reconstruction. (c) Correlate OT results with clinical findings of rheumatoid arthritis in finger joints. (d) Optimize the performance of the OT imaging system to achieve minimal computation time.